Iontophoresis is a non-invasive method of propelling high concentrations of a charged substance, known herein as the active agent, transdermally by repulsive electromotive force using a small electrical charge. The active agent can include a drug or other therapeutic agent. The charge is applied by an electrical power source to an active electrode assembly placed on the skin which contains a similarly charged active agent and a solvent in which it is dissolved. Current flows from the electrode assembly through the skin and then returns by means of a return or counter electrode assembly also placed on the skin. A positively charged electrode assembly, termed the anode will repel a positively charged active agent, or anion, into the skin, while a negatively charged electrode assembly, termed the cathode, will repel a negatively charged active agent, known as a cation into the skin.
Over time, metal electrodes used in iontophoretic transdermal patches may become corroded due to electrochemical corrosion of the metal during current flow through the electrode. Corrosion can increase the electrical impedance of the patch, decreasing the current delivered from that patch to the skin with a resulting decrease in the delivery rate of therapeutic agents from the patch. There is a need for electrochemically corrosion resistant electrode materials used in iontophoretic transdermal patches.